I installed a 6" fabtech lift on my f350 superduty crew cab. The problem is I have tried for 2 weeks to get the carrier bearing shimmed right with no luck, I have tried measuring the angle of the front and back drive shaft to ensure the match. I have gone up and done in shim size. I also purchased the superlift spacer that is meant for a 6 " lift. no luck with that. I have heard a 1/4" per inch of lift and an 1/8" per inch. but no luck there either. Any suggestions or does anyone have the size shim that worked for them?

 

I believe you should be about 1/4" per 1" of lift. If you purchased a 6" lift determine the "actual" amount of rear lift you installed. A 1-1 1/4" spacer should put you close. There is no exact specification here as too many variables are involved.

You want to check your rear axle pinion angle with the transfer case output pinion, not the driveshaft. This should be done with a relatively acurate analog or digital protractor.

I assume your complaint is a vibration issue?

Has the shaft been removed from the vehicle? If removed and not returned in it's orig position it maybe out of phase causing vibration. Have you confirmed all your joints are ok, or were any replaced ? It also may require balancing.